1. Field of the Invention
The present invention relates to an apparatus for measuring brightness, and more particularly relates to a method and an apparatus for precisely measuring the brightness of a device having a light-emitting display unit.
2. Description of the Prior Art
A light emitting diode (LED) or an organic light emitting diode (OLED) located in a laser telescope is used to display a reticle and a distance value between a target object and the laser telescope. Generally, an original brightness value of the LED or the OLED is offered by manufactory, but it isn't always precise. In the laser telescope, the light of said reticle and the distance value which are displayed on LED or OLED needs to pass through several lenses, for example a focusing lens, a prism group and a ocular lens etc., and then they are observed by user. The factual brightness of the light entering the eyes of user will decline because the lenses of the laser telescope can absorb and reflect the light. In other words, there is a difference between the factual brightness of the light observed by the eyes of user and the original brightness of the LED or the OLED, thereby the original brightness value of a light-emitting display unit offered by manufactory can't be taken as a basis to estimate whether a product having the light-emitting display unit is according with standard.
Otherwise, if the factual brightness value is estimated directly by the eyes of user, it is inconsistent and imprecise because of a difference caused by users' sense of sight. For quantizing the factual brightness of a device having the light-emitting display unit, one conventional solution is to utilize a luminance meter or a spectroradiometer to measure. However, it is very difficult to measure the factual brightness value of the LED or the OLED in the laser telescope using these prior apparatuses, because an area of the light projected by the LED or the OLED is very small. Additionally, these apparatuses are very expensive and not fit to be utilized in a scene of mass production.
Hence, a method to overcome the above-mentioned disadvantages of the prior art will be described in detail in the following embodiments.